Transferrin, the serum iron binding protein is responsible for the exchange of iron between sites of assimilation, storage, and utilization. For each iron bound to transferrin, one CO3 2 minus or other synergistic anion is required. The chemistry of iron and anion is dequired. The chemistry of iron and anion exchange by transferrin is of prime importance to chelation therapy in iron overload and as a model for studying other metal ion exchange reactions in biological systems. The proposed research is divided into seven topic areas as follows: 1. The removal of Fe2 3 plus from Fe3 plus transferrin-CO3 2 minus by chelating agents; 2. The exchange of anions by Fe 3 plus -transferrin-anion complexes; 3. The oxidation of Fe 2 plus and reduction of Fe 3 plus bound to transferrin; 4. Fe 3 plus sequestering activities of apotransferrin; 5. Nonspecific serum iron complexes and their reaction with apotransferrin; 6. Nonferrous metal ion binding and exchange by transferrin, and 7. Interactions of metal-transferrin-anion complexes with the reticulocyte and its ghost.